Blanca mushroomed into a major hurricane off Mexico's Pacific coast on Wednesday but could weaken before making a weekend landfall in the tourist-friendly Baja California peninsula, forecasters said.

The storm's maximum sustained winds reached 210 kilometers (130 miles) per hour and was in a stationary position some 675 kilometers (420 miles) southwest of Zihuatanejo, Guerrero state, according to the US National Hurricane Center.

Blanca became a category four hurricane, the second most powerful on the five-level Saffir-Simpson scale.

The center's tracking map shows Blanca striking the southwestern coast of the Baja California peninsula as a tropical storm on Sunday, the same day that Mexicans vote in congressional and municipal elections.

Blanca would make landfall north of the Los Cabos resorts that were ravaged in September by Hurricane Odile, which caused millions of dollars in damage and left six people dead.

Authorities in Los Cabos said they were monitoring the storm's progress.